The combination of TpTiCl(2)(OR) (Tp = Hidrotris(pyrazolyl)borate; R = Me, Et, i-Pr, n-Bu) precatalysts with methylaluminoxane (MAO) produced active catalysts for styrene polymerization. In general, these precatalysts showed higher activities than TpTiCl(3). The activity and syndiospecificity of TpTiCl(2)(OR) were affected by alkoxyl ligands. The syndiotacticity of the polystyrenes (s-PS) obtained was in the range of 47-70%.